Re: I have a subjestion

[Tom N Harris <telliamed@...>]

On Monday, April 07, 2014 09:37:38 AM jesus manuel Castillo blanco wrote:
> I have a subjection that you may want to consider, you have chosen to use
> callbacks function in the C style because you needed to allow multiple
> callbacks to be allow and C++ make this difficult, so I thought you make
> want to use the method on the link bellow that I was discussing with some
> guys of about passing C++ methods pointer. I realized that it may be a bit
> risky but so is passing C callbacks with the advantage that now I don't
> have to create a function that some how has access to a instance of a
> class. I think this would make LUA easier to use.
> 
> http://stackoverflow.com/questions/20359668/is-it-safe-to-calling-a-member-f
> unction-not-defined-on-the-base-class-from-of-a

Aside from the tautological reason that C callbacks are used because Lua is 
written in C, it is also the most portable callback style that can be adapted 
to any language. A bound method pointer is only callable from C++ code and 
would require that Lua be built by a C++ compiler.

There are C++ wrapper libraries like Selene[1] that take care of interfacing 
your C++ objects with plain Lua.

A simplified way of calling a method on a class would be:

    class Frobulator {
        int Sworl();
        void tolua_Sworl(lua_State* L) {
            lua_pushlightuserdata(L, this);
            lua_pushcclosure(L, &fromlua_Sworl, 1);
        }
        static int fromlua_Sworl(lua_State* L) {
            Frobulator* self = 
                (Frobulator*)lua_touserdata(L, lua_upvalueindex(1));
            lua_pushinteger(L, self->Sworl());
            return 1;
        }
    }

A more complete implementation would use metatables. But as I said, there are 
libraries that do all this for you.

[1] https://github.com/jeremyong/Selene

-- 
tom <telliamed@whoopdedo.org>